1980 cb 750 starting

[h500r]

battery spins bike over nice when cold
after 1/2 hr running , when motor is up to temp
shut bike off , try to restart , bike barely turns over
charging system is working , 12.8 volts in battery
it does not want to turn over , let engine cool it spins right over
seems like something is getting tight when hot
anyone ever come across this problem ?
thanks
greg

[dylansdad022102]

starter could be shot? never really heard anything like that before

when the starter heats up  the bearings are probably soft seizing.